The invention relates to a method of transferring charge from a first capacitance to a first point via a transistor circuit which exhibits a first threshold level, at least during said transfer to the first point.
Such a method is inter alia used in the so-called bucket brigade memories (see for example IEEE International Solid State Conference, Feb. 19, 1979, Digest of Technical papers, pages 74, 75 and 185). This known method suffers from the limitation that only charge packets of one specific polarity can be transferred.
Another method of charge transfer is employed in the so-called switched capacitance integrators which are used in integrated filters (for these see for example IEEE, J.S.S.C. vol. SC-13, No. 6, December 1978, pages 906-909). In such integrators, charge packets are formed on a capacitance, which packets are switched to a capacitance which is connected across an operational amplifier for the purpose of negative feedback. Such an integrator inter alia has the drawback that one operational amplifier per integrator is required, which operational amplifier continuously dissipates energy and generates noise and takes up comparatively much space in an integrated circuit.
A third example of the use of the method mentioned above is a charge read-out amplifier which is inter alia employed for the nondestructive readout of charge coupled devices (CCD) (for these, see inter alia IEEE Transactions on electronic devices, Vol. ED-23, No. 2, February 1976, pages 133-142). In this read-out amplifier the mirror charge of an input capacitance flows to a capacitance which is connected across an operational amplifier for the purpose of negative feedback, after which the charge on the negative feedback capacitance can be restored by short-circuiting said capacitance. This known application inter alia has the same drawbacks as the said integrators.